To the south of the road between Stanton St Bernard and Alton Barnes on the perimeter of what was the Alton Barnes Airfield I noticed a large sarsen stone which I hadn't noticed before. As this is on the route that I believe the sarsens took from the Marlborough Downs to Stonehenge I went to investigate.
The site is recorded on Pastscape at http://www.pastscape.org.uk/hob.aspx?hob_id=1422290
and can be found on the Defence of Britain database as http://archaeologydataservice.ac.uk/archives/view/dob/ai_full_r.cfm?refno=6470
There is an excellent Google Earth kmz downloadable of the Defences of Britain from http://archaeologydataservice.ac.uk/archives/view/dob/download.cfm